1. Field of the Invention:
The present invention relates to the preparation of ortho-hydroxybenzyl alcohols, and, more especially, to the preparation of ortho-hydroxybenzyl alcohol, commonly known as saligenol, by the condensation of either formaldehyde or a formaldehyde-generating compound with esters derived from boric acid and from phenol or substituted phenols.
2. Description of the Prior Art:
Ortho-hydroxybenzyl alcohols are desirable intermediates for the preparation of the ortho-hydroxymethyl-phenylacetic acids which are useful as plant growth regulators. Saligenol itself is an important industrial product both for its pharmacological properties and as an intermediate for the synthesis of insecticides.
The presently most valuable industrial process for the manufacture of ortho-hydroxybenzyl alcohols consists of reacting formaldehyde or one of its derivatives with an aryl metaborate; compare U.S. Pat. Nos. 3,290,352 and 3,290,393 and French Pat. No. 1,328,945, each hereby expressly incorporated by reference in its entirety and relied upon. This process provides saligenol in yields on the order of 65%, expressed relative to the phenol and the formaldehyde employed in the reaction. Despite its value, it has been determined that this process is not without disadvantages from an economic point of view. In fact, in a process of this kind, the formaldehyde which is not converted to saligenol is lost in the form of by-products and/or cannot be recovered from the reaction mixture. And insofar as the boric acid is concerned, although same is not converted in the reaction process, it too is lost because the recovery of same would require the use of expensive isolation techniques. The loss of these two products consequently contributes to an increase in the cost of saligenol.